Haryana PMT Haryana PMT Solved Paper-2007

  • question_answer
    The inductance of a coil is L = 10 H and resistance R = 5 \[\Omega \]. If applied voltage of battery is 10 V and it switches off in 1 millisecond, find induced emf of inductor.

    A) \[2\times {{10}^{4}}V\]                                

    B)  \[1.2\times {{10}^{4}}V\]

    C)  \[2\times {{10}^{-4}}V\]                              

    D)  None of these

    Correct Answer: A

    Solution :

                    Amount of magnetic flux linked with inductor is \[\phi =Li\] Now, the emf induced in the inductor is given by                 \[e=-\frac{d\phi }{dt}=-\frac{d}{dt}(Li)\] or            \[e=-L\frac{di}{dt}\] or            \[|e|=L\frac{di}{dt}\] Here, induced current \[=\frac{V}{R}\]                                                 \[=\frac{10}{5}\]                                                 \[=2A\] Circuit switches off in 1 millisecond or            \[dt=1\times {{10}^{-3}}s\] and        \[L=10H\] \[\therefore \]  Induced emf in inductor is \[|e|=10\times \frac{2}{1\times {{10}^{-3}}}=2\times {{10}^{4}}V\]


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